1. Field of the Invention
This invention relates generally to personal care devices for grooming hair and more particularly to hair curlers and devices for heating hair curlers.
2. Description of the Related Art
Hair setting and curling devices are well known that include means for heating hair rollers to a selected temperature for use in the curling or setting of hair. These devices usually comprise a casing that has supports for detachably holding and heating hair rollers. When the rollers are heated to a desired temperature they are removed from the supports. The user winds a cluster of hair around the outer surface of the heated roller and as a result the hair is more readily curled. The roller may be removed from the hair after several minutes.
An example of a hair roller as described above is shown in U.S. Pat. No. 3,600,552 issued to Tolmie for portable electric appliance. The Tolmie Patent discloses a hair setting and curling means including hair roller means and heating apparatus therefore. The heating apparatus is provided in a casing that includes a heating plate having a plurality of spaced and parallel rail members. Hair rollers are provided that have grooves in one end adapted to be fitted over the rails, thereby enabling heat to be conducted from the rail members to the rollers.
Another example of a hair roller heating appliance as described above is shown in U.S. Pat. No. 6,114,661 issued to Anthony Leung for a hair curler with slot adapted to receive a rail-like heat conductor. The Leung Patent discloses hair rollers assembled from a pair of semi-cylindrical members where each hair roller is configured to fit over a rail-like heating apparatus. An electrical heater in the shape of a bar is arranged to receive a plurality of hair rollers for heating thereon.
The Tolmie device is inefficient because heat must be transferred from the heater element to the heater case and then from the heater case to the heater rails holding the hair curlers. Heat is lost at each heat transfer interface. The Leung device improves upon the Tolmie device by forming the heating element into a rail-like configuration over which the hair rollers are placed. In the Leung configuration heat is transferred directly from the heating element to the hair curlers. However, the Leung device has the disadvantage of including a cross-wise slot through each hair roller. The heating element passes through the slot, thereby exposing any plastic portions on the exterior of the hair roller to high temperatures. These high temperatures can damage or melt the plastic, limiting the materials available for the exterior of the hair roller. Further, the transverse slot through each roller potentially entangles hair wound around the roller. More importantly, heat energy generated by the heating element is lost to the air where the heating element extends between hair curlers disposed thereon.
Accordingly, a need exists for a more effective heating arrangement in which the path of heat conduction to a hair roller is as short as possible, minimum heat energy is lost and in which the hair roller is of a cylindrical configuration.
An object of the invention is to provide a new and improved hair curler-heating appliance which quickly and efficiently heats hair curlers.
Another object of the present invention is to provide a new and improved hair curler heating appliance which receives and supports hair curlers of cylindrical configuration.
A still further object of the present invention is to provide a new and improved hair curler heating appliance of energy efficient design.
These and other objects of the invention are achieved by a hair curler heating appliance in which each of a plurality of resistive heaters is disposed in a heater tube which is in turn received in an axial cavity of a hair curler. This arrangement generates heat precisely where it is needed and leaves no part of each heater exposed to dissipate heat. Thus, minimum electrical energy is required to heat a plurality of hair curlers to a desired temperature.
A base plate supports multiple heater tubes in a compact, staggered arrangement. A thermostat is arranged to sense the temperature of the base plate and disconnect electrical energy from the base plate when a pre-determined temperature is reached. The relationship of base plate temperature to heater tube temperature is known, permitting the thermostat to be calibrated.